1. Technical Field
The present invention relates to an image reader and more particularly an image reader including a reading unit for optically reading an original mounted on an original mounting plate in an original reading area.
2. Related Art
There is an image reader for reading an image from a transmission original and carrying out electronic information processing of image information. As this image reader, for example, there is known an image reader which includes an original mounting plate which is formed of flat glass for mounting an original and a reading unit for optically reading the original mounted on the original mounting plate from the original mounting plate side, reads an image from the mounted original and carries out electronic information processing of image information.
For example, in an image reader disclosed in JP-A-2000-113162, the reading unit which is a contact image sensor reads white and black specific patterns provided at the outside of an original reading area for reading the original so as to detect a read start location when the reading unit reads the original and the location of a home position waiting before the reading unit starts to read the original.
The specific patterns of the image reader described in JP-A-2000-113162 are formed on a frame surrounding the original mounting plate for mounting the original, for example, by offset printing, but an error in millimeter unit may occur between an actual formation location and an accurate formation location in design. Accordingly, in this case, the same error occurs even in the read start location and the location of the home position detected by reading the specific patterns using the reading unit.